So I was curious about parallel circuit. I first built four branches and only filled them with three light bulbs. Surprisingly, it looks something weird like the picture below. When I filled the fourth branch with a light bulb, everything light equally and even brighter.

Okay, here's what I know. I know that the wire that is outside the branch and connects with the fourth branch, has more current for sure because there is no resistance. However, why the first light bulb got brighter than the second one and so on. Secondly, why is the circuit with 4 light bulb is brighter?